The present invention relates to a pressure gauge, and more particularly to a pressure gauge with two detecting heads.
FIG. 1A is a partially sectional view of a prior art example of a pressure gauge with two detecting heads and FIG. 1B is a partially enlarged view of a preferred embodiment of the same pressure gauge. According to the prior art, a pressure gauge with two detecting heads for measuring the pressure of a tire includes a hollow cylinder tube A having passage a1 therein and an annular projection G which has two opposite ends, each provided with an annular thin protrusion T; a spout portion H having a passage a2 therein, connected to the hollow cylinder tube A; a sensing member F connected by threads to the spout portion H ; a pair of sealing plates D1 and D2 having a circular shape with holes D11 and D21 in the middle of the plates and respectively disposed on the protrusion T; an elongated rod B having two opposite ends and tip portions C1 and C2, respectively and movably fitted on the open ends of the hollow cylinder tube and between the pair of sealing plates, the diameter of the holes D11 and D21 being smaller than the diameter of the elongated rod B. A pair of pressing member E1 and E2 having a circular shape and having holes therethrough is attached by threads to the cylinder tube A, one on each side. When in use, pressurized gas enters the apparatus through the tip portion C1, forcing the elongated rod B to one side , thus blocking the hole D11. The pressurized gas will pass through another hole D21 through the passage a1 and then to the passage a2 of the spout portion H and to the sensing member F. In this way one can measure the pressure of a tire.
But there are some drawbacks to the prior art device. First, the protrusion T in the prior art is very thin. To produce such an annular thin protrusion with a horizontal surface, requires very high precision in the manufacturing process. Poor machining of this one difficult to produce part however, results in inaccuracy in measuring the pressure of a tire. Second, if the protrusion is made a bit thicker, a higher pressure will be needed when engaging the pressing member and the cylinder tube. Third, the pressing member and the cylinder tube are connected by threads, as are the the spout portion and the sensing member, requiring additional labor, thus causing inconvenience and increasing the manufacturing cost.